**2.4 Type of closures (OTR)**

The last step in winemaking process is bottling. The main aim of this is to package the wine to get the customers in comfortable and attractive way and also to preserve the organoleptic characteristics of wines. Although it may seem the easier process step, it is critical to maintain and, sometimes, also to improve the qualities of the product over time until the consumption. On the one hand, wine should be prepared and fined to prevent chemical precipitations of salts, color matter, protein haze and microbiological alterations as well, always respecting the nature of the wine and their characteristics. On the other hand, the type of closure should be selected according the consumption time expected. Closures should assure that the contents do not drip out of the bottle and that the contents were not altered by oxygen. Nowadays, wine producers have several options to stopper wine bottles, such as screw caps, crown corks, plastic caps of grass closures with plastic sealing.

#### **Figure 4.**

*Production of volatile sulfur compounds in white wines bottled in different color of bottles (clear bottles; a) and green bottles; b)) after 10 days of exposure with six different types of LEDs compared with darkness condition.*

Several changes can take place in wine after bottling, some of them desired and expected as increasing of complexity, roundness, pleasant and desired evolution. Anyway, also unexpected changes derived from stoppers can also occur due wine oxidation or reduction [43]. Some of these unexpected changes can modify the quality of wines and, in the worst case, these wines could be considered defective products and often undrinkable.

One of the factors with more influences in wine aging and evolution is oxygen. Oxygen is trapped in the headspace of the bottle after bottling, it is present in the wine dissolved and also permeates through the closure combined with temperature and light, modifying the oxidative status of the wine during storage [44]. So, winemakers have the option to modify and control the evolution of their wine after bottling selecting the closure type. The flow of oxygen able to pass through the closure of a wine bottle is referred to as OTR (oxygen transmission rate in 24 h). This parameter depends on the thickness of the material and the partial pressure gradient between the atmosphere of the external environment and the headspace of the bottle [45]. This oxygen ingress is typically slower than the rate of oxygen consumption of the wine, so that, after consumption of the initial excess of oxygen, dissolved and headspace concentrations of oxygen are usually very low (often micrograms per liter) [46]. Other common indicator in oenology is the total package oxygen (TPO) which can vary over a range of approximately 1 and 9 mg/L. This parameter consist of the sum of two components, wine dissolved oxygen and headspace concentration [33].

Different OTR ranges could be found in bibliography, detailing the approximately oxygen transmission rate for each type of closure. Screw cap saranex and screw cap saran tin are the closure options with lower OTR values with 0.0006 and 0.0008 mL of O2 per day, respectively (AWRI measurements) [47]. Micro agglomerate technical corks with a very low OTR could get similar values as screw cap close to 0.0006 and 0.0007 mL of O2 per day, natural corks increase slightly the permeability till between 0.0002 and 0.006 mL O2 per day (Jim Peck's MOCON measurements) Finally extruded synthetic closures showed a higher permeability around 0.0019–0.0030 mL O2 per day (Jim Peck's MOCON measurements).

In the studies carried out at VITEC, the volatile composition responsible for the reduction aromas was evaluated taking into account the use of five corks (from C1 to C5) with different OTR values (OTR values from C1 to C5 was of lower a major) in sparkling white wines throughout 3, 6 and 12 months of aging in bottle. A crowncap (CAP) was used as control wine (**Figure 5**). As can be seen in this figure, the control samples with CAP stoppers and C1 corks with the lowest oxygen transmission (OTR), were the ones with the highest concentrations of thiols, sulfides and disulfides, mainly after 12 months (12 M) of aging in the bottle.

#### **2.5 Type of bottles**

As stated previously (**Figure 4**), another very important factor in the wine bottling step is the choice of the container in which the wine will be stored until its consumption. This container or packaging must take into account the protection and conservation of the product. In the case of wine there are different types of containers such as the tetra brick which is a cardboard for drinks made up of different layers of polyethylene, paper, and aluminum; the bag in box consisting of a polyethylene bag and a tap with a valve for dosing it; PET (polyethylene terephthalate) plastic containers; aluminum cans type; and finally, the most widely used container in the world in the case of wine, glass. Which is a mineral product obtained by fusion and that solidifies without crystallizing. It is also an inert material, and from an environmental point of view it is favorable because it is a fully recyclable material.

*The Light Struck Taste of Wines DOI: http://dx.doi.org/10.5772/intechopen.99279*

**Figure 5.**

*Concentrations of thiols, sulfides and disulfides in sparkling white wines stopped with 5 different types of corks and cronw-CAP (CAP), over 3, 6 and 12 months of aging in the bottle.*

Nowadays, different shapes of glass bottles are used (Bordeaux, Burgundy, Champagne, Rhin, Jerez, Porto) with different capacities, and of different color and shade of glass (flint, amber, green, blue, etc). The choice of the color of the glass is of great importance with regard to the preservation of wine during storage or aging. This is due to the fact that the incident light in the bottles penetrates through the glass, producing oxidation–reduction reactions in the wine and consequently affecting its organoleptic qualities. Glass wine bottles only transmit wavelengths greater than 300 nm [6]. Standard clear bottles (flint) generally transmit more than 80% of visible UV radiation above 360 nm, while clear bottles with additional UV protection, which are made by adding a UV absorbing species to glass or by coating clear bottles with a film that contains a species of this type, transmits less UV radiation [48]. Green bottles transmit considerably less light than clear ones, particularly in the region below 520 nm, while amber bottles transmit very little radiation below 520 nm. For the darker colored bottles, the heavy bottles, which have thicker glass, transmit slightly less light than the lighter counterparts.

#### **2.6 Aging and time of light exposure**

It is well known that wine is very sensible to temperature which can directly affect their global quality [49]. Temperature can play a significant role impacting directly to the color, aroma and mouthfeel accelerating their natural aging process. Ideally, wines should be stored in conditioned rooms in cellars normally with air conditioned facilities (15–20°C). However, wine could experiment changes in their temperature being exposed to less optimal conditions, especially during transport or storage distribution process [50]. Visual affectations could also be observed, being the most notable the formation of a haze resulting from the denaturing of proteins in rosé and white wines [51]. If temperatures are so high and wine it is packaged in glass bottles the temperature effects can include cork push due to the volumetric expansion of the wine impacting directly to closure seal integrity and

**Figure 6.**

*Degradation of riboflavin in a white wine bottled in a clear bottle and in a green bottle after 10 days of exposure to 6 different LEDs.*

impacting in oxygen transmission rate (OTR) [52]. Several published studies detail the changes showed by wines when these are exposed to high temperatures, and other composition variables as pH, SO2 concentration, alcohol content, tannins concentration or others [3, 37, 53–58].

Several authors as studied the direct effect of temperature on the volatile composition of red and white wines [59]. Over a 21-day period, the study found that a constant 40°C heat treatment had a greater impact on the aroma and volatile composition of the wines compared with that of the 20°C/40°C cycled treatment, which in turn had a greater impact on that of wines stored at a constant 20°C. These studies conclude that it is evident that as a direct result of heat, the fruity acetate compounds in the wines are disappearing and aged-like characters have developed. Temperature not only affects the volatile compounds, also non-volatile compounds as polyphenols experiment changes at high temperature. The most common effect on non-volatile in red wines is a decrease in anthocyanin concentration and a corresponding increase in tannin-bound anthocyanins.

Apart from the temperature, the light incidence is also an important factor to take into account during the aging period. As mentioned above, the susceptibility of white wines to produce the LST has been mainly associated with the photosensitizer riboflavin and the produced unpleasant odor has been attributed primarily to volatile sulfur compounds. Maujean found that hydrogen sulfide, methanethiol, and dimethyl disulfide were formed in Champagnes exposed to a solar simulation lamp in glass cuvettes, in the absence of oxygen [28]. In our study (**Figure 6**), the degradation of RF was found just after 10 days of exposure to light in white wines bottled with green and clear bottle body. As can be seen in **Figure 6**, the white wine with a clear bottle presented large decreases of RF. More than 50% of the initial content in clear bottles and more than 30% in gree bottles in the case of L.A. The white wine bottled in clear glass showed a degradation of riboflavin with more types of lights.

## **3. Analysis of the main chemicals related to LST**

To evaluate the aromatic defect that we are dealing with, it is necessary to know which compounds could be responsible but, to know the contribution of each one to wine aroma, it is also necessary to know their concentration. In addition, to have a better control of this problem, it would also be very interesting to obtain information on the concentration of the precursors since their degradation provides the unwanted volatile sulfur compounds (VSCs). However, since from a physicochemical point of view the precursors are chemical compounds very different from the VSCs, both the sample preparation techniques and the analytical techniques will be also different in each case.
